The present invention relates generally to components of large printing presses, and in particular, to an advantageous construction and arrangement of controls for the "page pack" portion of the system used to deliver ink to the inking rolls of such large printing presses.
By way of background, the mechanism used to ink the rollers in large scale, high speed printing presses, such as those used to print daily newspapers, has several important components, namely, an orifice plate, an ink rail and several ink pump assemblies. The orifice plate receives a supply of ink from a pumping system and forms and positions a film or bath of ink adjacent the inking roller of the press, which in turn picks up the ink and transfers it to an impression roller.
The ink rail component usually supports four pump assemblies by positioning the pump housings in a desired relation to the other components. Each pump housing customarily positions six or eight ink pumps, one for each column of the page being printed. Cumulatively, the housing and one set of ink pumps, their associated drive mechanism, the drive controls, and the associated fittings and manifolding are sometimes called a "page pack." Here, a page pack is contained within the width of one page of a newspaper, i.e., approximately 13-14 inches.
In presses dating back several years, the ink pumps themselves were of a valveless, positive displacement type pump utilizing rod-like piston with a chordwise relief on one end, movably received in a ported cylinder. The piston rotated and reciprocated within the cylinder, drawing in and expelling ink through inlet and outlet ports. These pumps are constructed and arranged in a known manner such that with one portion of the working cycle, the piston is withdrawn at the time the relief is indexed with an inlet passage. This withdrawal motion pulls ink by suction through the inlet port and into a closed end working chamber. In a second portion of the operating cycle, the piston strokes back towards the closed end of the cylinder at the same time its rotary motion indexes the relief with an outlet port in the opposite side of the cylinder. This movement causes the ink that has just filled the working chamber of its cylinder to be displaced outwardly through the exhaust port. As the rotation and reciprocation of the piston continue, this cycle is repeated.
In the recent past, approximately 10 or more years ago, the drive mechanism for some of these pumps was changed significantly. In the older style pumps, a mechanical master drive system operated through a power train of gears and shafts to rotate and stroke the ink pump pistons. Volume control was achieved by varying the angle between the driving and the driven elements. Because pump output per cycle is dependent on the effective angle between the rotational axes of the piston and cylinder on the one hand and the driving member on the other hand, some sort of angle-changing mechanism was required.
The prior art used complex mechanical arrangements for varying this effective angle (minimizing the angle down to and including zero when pump output was to approach and reach zero), and such arrangements created significant maintenance and quality control problems as well as being expensive initially.
Because the industry recognized its many shortcomings in the approach of changing ink pump output rate by varying the driving member/driven member angle as explained above, a different kind of drive system was developed some years ago. This system provided individual electric drive motors for each pump assembly instead of using a common drive source. Now, volume control is achieved on a continuous basis by utilizing a stepping motor for each pump, and an electronic digital control arrangement. Such an arrangement is sometimes termed a "digital" page pack.
In this arrangement, one output pulse from a driver circuit causes the stepping motor to move one step, and this in turn causes the pump to rotate a very small fraction of one complete rotation. Typically, one complete 360.degree. revolution requires 300 to 400 individual steps, and hence, in the case of a 400 step motor, 400 individual pulses would be required to achieve one rotation.
The time interval between pulses determines the rate; the longer the interval, the slower the rate. The advantage of such a control system is that both true zero movements as well as very minute pump movements may be achieved.
With a system wherein the page pack includes six or eight stepping motors and six or eight pumps, each motor can be driven at its own rate, entirely independently of the rate of any other motor. This rate is established by the operator, and control of each pump rate is achieved by inputting signals at a control keyboard. Accordingly, a microprocessor keyboard can be used to set the output rate of each of the individual pumps, thereby varying the amount of ink fed to a counterpart portion of the orifice plate with each pump revolution. Thus, if the impression cylinder printing a newspaper page had a large ink requirement near the center of the page and a great deal of "white space" near the margins, then the individual pumps near the center of each page pack will be made to operate at a relatively higher rate to furnish more ink in keeping with the requirements of the inking roller, whereas the peripheral pumps would operate at a lower or zero settings because the ink demand for a white space area of the paper is much less.
Referring now to the aspect of overall press speed, the amount of ink consumption for a given ink density is also directly proportional to press speed, which itself is variable. In this connection, a second advantageous feature of the above stepping motor control arrangement is that the overall, real-time frequency of these stepper motor drive pulses may be increased or decreased by an overall rate controller which is in turn slaved to or governed by a tachometer system. Accordingly, once the relative control rate for the individual pumps is set, ink delivery at a certain rate is assumed. However, if the press speed as a whole decreases, then it is necessary to decrease the rate at which all of the individual ink pumps operate in order to compensate for the reduced ink demand. The converse is true; in the event the press begins running at a comparatively higher speed, the rates of all the pumps must increase in direct proportion to press speed.
Accordingly, known control systems am able to establish a series of settings which establish the relative rate flow of the individual ink pumps within all of the page packs, and these relative settings are kept proportional to press speed by a tachometer system that takes actual press speed into account.
Even with the improved page packs of the type just referred to, there has been a need for further improvement, inasmuch as the reliability and maintainability of such systems has not been as great as might be desired. In this connection, it must be realized that considering the enormous number of impressions made by newspaper printing presses, and the requirement that daily papers be printed on an almost continuous basis, the need for high reliability cannot be over emphasized.
In prior arrangements, over a particular period of time, a few of the output driver units typically operated almost continuously, while other driver units operated only intermittently or sometimes not at all. Thus, each of the driver chips developed a different temperature rise. Although the heat sinks associated with these chips were adequate under some conditions, it is accepted that lower temperature operation is more favorable to durability and reliability than is operation at or near the peak permissible operating temperature of the output driver chips.
In these past arrangements, particularly where the array of chips was located adjacent a keyboard or other control remote from the pumps and motors, favorable heat dissipation arrangements were not able to be achieved. It would be desirable if a heat sink arrangement could be made such that the temperature rise in certain chips would still be relatively modest even if such chips were operating continuously. By providing the combination of a greater heat sink capacity, as well as the ability to spread or dissipate the heat, particularly to those areas which am inherently cooler-running, better reliability is possible.
According to the invention, the arrangement of the driver chips on the board can enable the mass and the inherent heat capacity of the pump housing to be utilized in such a way as to improve reliability and serviceability of the electronic components in the page pack.
According to the present invention, it has been found possible to do away with remote positioning of certain parts or components of the control system, whereby only the keyboard and a few other elements need be positioned near the operator or pressman, while the others can be positioned adjacent the page pack, i.e., near the individual pumps and motors. In this arrangement, better packaging, and especially better control of generated heat, can be achieved, resulting in increased longevity and decreased service requirements. Thus, certain elements of the ink control system, particularly the motor and pump housings and the printed circuitboard comprising most of the motor control and drive circuits can be effectively arrayed to achieve optimum temperature rise control. In this way, their reliability can be significantly increased. According to the invention, an improved arrangement of packaging for these components has been provided with such arrangement being economical, effective and achievable at modest cost.
In view of the failure of the prior art to provide printing ink pump packages of optimum reliability and economy, it is an object of the present invention to provide an improved digital page pack, or pump-motor-and control system for printing press ink pumps.
A further object of the invention is to provide a component mounting arrangement with improved control of electrically generated heat.
Another object of the invention is to provide an improved page pack wherein a single housing for the pumps positions the motors and also includes a flanged body and a master heat sink rail that is in intimate heat exchange relation with the heat sinks on the output drivers for the stepping motors used to control the ink pumps.
A still further object of the invention is to provide an arrangement whereby, on a printed circuitboard type control assembly, plural high current output driver units, each having its own small heat sink, are arrayed in a common plane and arranged to be fastened to a metal element serving as a master heat sink.
Yet another object of the invention is to provide an arrangement of heat sink materials, including a portion which is integrally cast with the page pack pump and motor housing and another master heat sink portion which may be fixed to the integrated heat sink elements on the output drivers and thereafter placed in intimate heat exchange relation with the remainder of the housing.
A still further object of the invention is to provide a control system for an array of printing press ink pumps which includes housing having openings for receiving ink pump and the output shafts of individual drive motors, a mounting surface for the drive motors, and end and sidewall housing flanges, with each flange including a slot for receiving a circuitboard, and with one flange including a master heat sink mounting surface, so that with the margins of a circuitboard disposed within and positioned by the slots, the master heat sink can be fastened both to the individual heat sinks forming a part of the circuitboard and to flange on the housing.
Another object of the invention is to provide an improved arrangement for component mounting in an ink pump system, wherein the control system includes a remote keyboard, pump drive circuitry on a circuitboard, with the drive components of the circuitboard being positioned adjacent the pump motors and in intimate heat exchange relation with the housing for the motors.
The manner in which the foregoing and other objects of the invention are achieved in practice will become more fully apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, wherein like reference numbers indicate corresponding parts throughout.